Department of Applied Physics, Aalto University , P.O. Box 11100, FI-00076 Aalto, Finland.
Department of Bioproducts and Biosystems, Aalto University , P.O. Box 16300, FI-00076 Aalto, Finland.
Biomacromolecules. 2017 Feb 13;18(2):374-378. doi: 10.1021/acs.biomac.6b01396. Epub 2017 Jan 31.
The ultrastructural organization of cellulose elementary fibrils (EFs) in wood cell wall is considered to be the prime factor regulating the material characteristics of wood in micro to macro levels and the conversion of delignified wood fibers into various products. Specifically, the complex assembly of EFs in wood cell wall limits its swellability, solubility, and reactivity, for example, in dissolution of cellulose for regeneration of textile fibers, fibril separation for the manufacture of nanocellulose, and enzymatic hydrolysis of cellulose into sugars for their subsequent fermentation to various products, like ethanol for future fossil fuels replacement. Here cryo-transmission electron tomography was applied on ultrathin spruce wood sections to reveal the EF assembly in S layer of the native cell wall. The resolution of these tomograms was then further enhanced by computational means. For the first time, cellulose in the intact cell wall was visualized to be assembled into helical bundles of several EFs, a structural feature that must have a significant impact on the swelling, accessibility, and solubility of woody biomass for its conversion into the aforementioned value added products.
木材细胞壁中纤维素基本原纤维（EFs）的超微结构组织被认为是调节木材在微观到宏观水平上的材料特性以及将去木质化的木纤维转化为各种产品的主要因素。具体来说，木材细胞壁中 EF 的复杂组装限制了其溶胀性、溶解性和反应性，例如在溶解纤维素以再生纺织纤维、分离纳米纤维素的原纤维以及酶解纤维素成糖以进一步发酵成各种产品，如乙醇以替代未来的化石燃料。在这里，冷冻传输电子断层扫描被应用于超薄云杉木材切片上，以揭示天然细胞壁 S 层中 EF 的组装。然后通过计算手段进一步提高这些断层扫描的分辨率。这是首次观察到完整细胞壁中的纤维素组装成几个 EFs 的螺旋束，这种结构特征必然对木材生物质的溶胀性、可及性和溶解性产生重大影响，以将其转化为上述增值产品。
